In recent years, disk devices such as magnetic disk devices and optical disc devices are widely used as external storage devices for computers and image recorders.
As a disk device, for example, the magnetic disk device generally includes a magnetic disk provided in a base, a spindle motor configured to support and rotate the magnetic disk and a suspension assembly configured to support a magnetic head. The suspension assembly includes a suspension attached to a distal end portion of an arm, a trace member (flexure, wiring trace) disposed on the suspension, and a load beam. The magnetic head is supported on a gimbal portion of the trace member, thus forming a head suspension assembly.
In recent years, such a suspension assembly has been proposed, in which a piezoelectric element (PZT element) as a drive element is mounted in the vicinity of the gimbal portion of the trace member, and thus the magnetic head is minutely displaced in a seek direction by expansion/contraction of the piezoelectric element. According to this suspension assembly, it is possible to finely control the movement of the magnetic head by controlling the voltage supplied to the piezoelectric element.
In the suspension assembly such as above, when the piezoelectric element expands or contracts by voltage application, the piezoelectric element may curve in the thickness direction. In this case, part of expansion or contraction of the piezoelectric element escapes in the curving direction of the piezoelectric element and the displacement (stroke) of the magnetic head decreases. For this reason, it becomes difficult to control the displacement of the magnetic head in line with the displacement of the piezoelectric element.